Telegraph system



May 12, 1942. P. HOLCOMB, JR

TELEGRAPH SYSTEM v 5 Sheets-Sheet 1 "IIIIIIiIIIIIFIIIIIllllllllllllllliifi;iwlllllllllllllllllllll Filed Dec. 7, 1939 nlllllu mun.

R J B RM ,Y O we 1 mm V H m /i 6 4 Y B G a Q 9 7 a 2 w a 8 4 c O 9 o FIG.

May 12, 1942. p HQLCQMB, JR 2,282,358

TELEGRAPH SYSTEM Filed Dec. 7, 1959 5 Sheets-Sheet 2 INVENTOR P. HOLCOMB JR.

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May 12, 1942. P. r-ioLcoma, JR

TELEGRAPH SYSTEM Filed Dec. 7. 1933 5 Sheets-Sheet 3 27 INVENTOR P. HOLCOMB JR.

May 12, 1942.

P. HOLCQMB, JR

TELEGRAPH SYSTEM 5 Sheets-Sheet 4 Filed Dec. 7, 1939 P. HOLCOMB JR May 12, 1942. P. HOLCOMB, JR

TELEGRAPH SYSTEM F iled Deo. 7, 1939 5 Sheets-Sheet 5 INVENTOR P. HOLCOMB JR.

v a large number of Patented May 12, 1942 TELEGRAPH SYSTEM Philo Holcomb, The Western Application December 7, 1939, Serial No.

Claims.

This invention relates to signalling systems and more particularly to expanding channel or varioplex telegraph systems wherein a channel or lane of trafiic is shared by a variable number of communication channels or sources of telegraph signals.

In a prior application Ser. No. 666,004, filed April 16, 1933, there is disclosed a telegraph system embodying the basic principle of the expanding channel system. The term expanding channel system as used herein refers to a systern in which a variable number of telegraphic transmitters or other sending devices are arranged to control receiving devices corresponding to each sending device over a lane of traffic, substantially the entire lane time in the preferred system being divided among the operative transmitters. The lane of trafiic preferably comprises a plurality of channels of a synchronous multiplex system but may comprise a single channel of such a system, one or more wire or carrier current channels or combinations of different types of communication channels. Hence the expression lane of traffic as used herein designates any suitable route or medium over which signalling is accomplished.

The expanding channel or varioplex system thus comprises a multiplex system in which the number of communication or subchannels operating over the connecting circuit or lane of trafiic may be expanded or contracted by cutting in or out transmitting and receiving devices, the operative channels sharing the lane of trafiic. The present invention relates particularly to a printing telegraph system of this character in which message characters are sent in sequence from one busy channel transmitter after another, omitting the idle or inoperative channels, although it is not limited to such systems.

The present invention is disclosed in a system which is related to the system disclosed in a, prior application of Philo Holcomb, Jr., Ser. No. 123,266, filed January 30, 1937, in which the apparatus employed for controlling the signalling channels is in large part mechanical. However, it is not contemplated that the present invention be limited to such a system. A telegraph system of this character is particularly useful to serve signalling channels each of which has a comparatively small amount of trafflC. In operation each of the sub-channels of an expanding channel system is in effect provided with a communication channel which is available for use at all times. The chief advantage of such a system is that the charges which are Jr., Great Neck, N. Y., assignor to Union Telegraph Company, New

York, N. Y., a corporation of New York made to a subscriber having such a, signalling channel may be based upon the actual use that such a subscriber makes of the signalling facilities. It is therefore possible to provide a subscriber with what in practice amounts to the equivalent of a private wire at rates which are materially less than the rates which would be charged for the exclusive use of a circuit between two distant points.

It is the practice to meter the traffic at the transmitting end of the circuit or, in other words, the point at which the traffic originates. Therefore, it is necessary to deliver at the receiving point all or substantially all of the trafiic which is transmitted. In order to accomplish this purpose it is necessary that the system be so arranged that there is a minimum probability of the transmitted trafiic being lost or mutilated in its transmission over the circuit.

Accordingly it is one of the objects of this invention to provide an expanding channel system which is so infallible in operation that equitable charges based on the number of message characters transmitted may be made to the subscribers of the various signalling channels.

Another object of the instant invention is to provide an expanding channel system in which periodic tests are made to insure the correct connection of corresponding transmitting and receiving apparatus.

Another object of the invention is to provide, in an expanding channel system, a means of testing the allocation of signalling channel apparatus which is operable over an auxiliary subchannel of the system.

Another object of the present invention is the provision of means for detecting incorrect allocation of channel equipment under certain conditions at times other than that of the periodic tests.

Another object of the invention is to provide means for metering the signalling channel traffic which is based upon the number of message characters transmitted, taking into account the simultaneous use of the lane of traffic by avariable number of other sub-channels. An advantage of such a metering arrangement is that the rate at which a subscriber is chargedfor service is in accordance with the simultaneous demands of other channels for transmitting time on the lane of traffic. It is obvious that at a time when the lane of traffic is in demand by a large number of channels, each unit of the transmitting time is more valuable than at a time when l a fewer number of the channel trafiic 3 drawings, of which:

, varioplex systems. For

channels require a share of the lane time.

It is another object of the instant invention to provide means for metering the signalling channel traffic, on the basis of the number of characters transmitted and the frequency of transmission. With a large number of channels operating over the lane of traflic, the frequency of transmission from any one channel is less than it is when a smaller number of channels is operating. Hence the frequency of transmission from any signalling channel is a measure of the busy condition of the lane of trafiic;

Another object of the invention is to provide a means of metering the trafiic of a signalling channel on the basis of the total operative time of the channel.

Another object of the instant invention is to provide a means for controlling the entry of a signalling channel so that the maximum rates which will be charged for the transmission of may be fixed at a rate selected by the subscriber.

Another object of the invention is to vision for giving a subscriber a means ling the maximum rates which he will for the transmission of his trafi'ic.

Another object of the invention is to provide means whereby a signalling channel may be entered only when the lane of traffic is being used by other sub-channels in numbers such that the rates are equal to a preselected rate and whereby a subscriber may have the advantage of any rate less than the preselected rate if the total number of signalling channels is reduced during his operative connection with the lane of trams.

Other objects and advantages of the invention will become apparent from the following demake proof controlbe charged scription of a system embodyingthe invention taken in conjunction with the accompanying Figs. 1 through 9 are views of one form of Figs. 10 and 11 illustrate diagrammatically the 1 mixer or .subchannel control device used in the a system embodying the invention;

Fig. 12 is a diagrammatic representation of the I circuits and apparatus of the receiving station.

A varioplex; or expanding channel, system fcomprises a plurality of channels which,'when operative, are selectively associated with a common lane of trafiic which, in the present embodiment, is constituted by a synchronous fourchannel or quad multiplex. Such a system utilizes a selector or mixer by which the operative gchannels are successively connected to the lane .in a prearranged order. The operative or inoperative conditionof a channel is automatically registered at the mixer so that its operation is governed in accordance with said conditions to divide substantially the entire lane time among the operative channels.

The system comprising the present invention utilizes a mixer. which is somewhat more mechanical in nature than those used in earlier each lane of traffic there is provided at the terminals a transmitting mixer and a receiving mixer. Figs. 1 through 9 illustrate the detailsof the transmitting mixer, the

I receiving mixer being substantially similar.

Referring to Figs; 1, 2and 3 and, for the moment, particularly to Fig. 2, a mixer arm forms-part of, oris secured to, a hollow hub 2|, which. is-rotated through a friction clutch 22 arm temporarily held ing to a channel which is to'be given a portion by a continually rotating shaft 23. The driven plate 24 of the clutch is characterized by a plurality of radial tongues 25 arranged in spaced relation peripherally of the plate and adapted to engage with vertical grooves 25 in the hub, whereby rotative motion may be transmitted to the hub, at the same time permitting axial movement thereof with respect to the driving shaft. Adjacent the extremity of the mixer arm 20 is a stop bar or latch member 21 pivoted at its upper lug 28 and having two operative positions, the one shown in full lines corresponding to a channel in condition and the one shown dotted corresponding to a channel out condition. The movements of the stop bar are limited by screws 29 and 30 to which electrical connections may be made. Maintenance of either stop bar position is obtained by the engagement of the lower lug 3| with a retaining member 32 which comprises a plunger 33 normally having the position shown, but which may be momentarily depressed against a spring by the lower lug as the stop bar is moved from one position to the other.

The stop bar 21, when depressed in its channel in position is in the path of the rotating mixer arm and consequently engages and pr vents further rotation thereof. With the mixer by a stop bar correspond of the lane time, the hub 2| is moved axially downward against the spiral compression spring 3 3. This downward movement is eliected by energizing the winding of the magnet 35 which attracts a pivoted fork 33 having pins 3? adapted to engage a circumferential channel 38 of the hub 2| and thereby transmit the motion of the fork to the hub and mixer arm 20. The depression of the mixer arm to the position shown dotted releases it from the stop bar 21- and permits further rotation which results in the engagement of the arm 2!) with a lever 39. This lever is pivoted by the rotation of the mixer arm until a stop pin 40 is engaged, the pivoting being sufficient forthe contact arm 4! to make or break (in this case break) a connection with a contact screw 42 and thereby connect the channel associated therewith to the lane of traffic as hereinafter described. Immediately thereafter the solenoid 35 is deenergized releasing the fork 36 and permitting the spring 34 to restore the mixer arm 29 to its upper position. It is thus disengaged from the lever 39 and continues its rotation until stopped by the next stop bar which is depressed in a channel in position.

One or more of the stop bars such as 21', best illustrated in Fig. 4, is provided with a spring S which normally urges the stop bar upward against its associated contact screw 29. Such a stop bar maybe selectively moved to its chanvpeded passage of the mixer arm 29 when the stop bar. is in its channel in position. The length of such a bar is suilicient topermit its being moved from its channel, out position-to stop bars such as 21" may its channel in position by the positioning means hereinafter described. However, it will become apparent that the apparatus disclosed herein is incapable of moving such a bar from its channel in position to its channel out position. It is contemplated that the restoration of a bar such as 21" to its channel out position is to be effected manually.

The functions and modes of operation of stop bars such as 21' and 21 are described in subsequent portions of the specification.

A plurality of such sets of stop bars and operating levers are arranged peripherally around the plane of rotation of the mixer arm 20 as may be seen in Figs. 1 and 3, each set corresponding to a channel which may have access to the lane of trafiic. A circular trench or groove 43 is formed in the stop surface of the insulating mounting 44 and imbedded therein is a wire or rod 45 (see Fig. 2) which is passed through the upper lugs of the stop arms and serves as the pivot therefor. This pivot rod also serves as a means of electrically interconnecting the stop arms and is held in the bottom of the groove by several screws, one of which 46 is arranged to termiate an electrical conductor.

Fig. illustrates one of i the channel operating levers 39a in a side elevation. Fig. 6 is a top view of the lever in position to be inserted into the mounting 44. 41 and an aligning slot in a bushing 48 (shown sectionally in Fig. 7). The projections 49 formed on the lever (see Fig. 5) are arranged to engage the upper and lower flanges of the bushing, thereby preventing endwise movement of the lever.

When the lever is fully within the bushing, it is given a counter-clockwise turn when viewed from the top, thus moving it out of alignment with the slot 41 and completing its positioning in the mounting. As illustrated in the partial side elevation of Fig. 4 and the plan view of Fig. 3, each operating lever 39 is normally held in contact with its associated contact screw 42 by means of a retractile spring 50 which is attached to the outer arm of one lever and to the inner arm of the lever succeeding it in the direction of rotation of the mixer arm 29. The retractile springs may also serve as electrical connections between the Various operating levers.

Facilities are provided for repositioning the stop bars of channels, the status of which changes during operation of the system. Assume that, in Fig. 2, the mixer arm 20 is engaged with the stop bar 21 which is associated with a channel to be disconnected from the lane. A solenoid 5| mounted within the upper portion of the hub 21 is energized and draws a plunger 52 downward. An arched leaf spring member 53, having one end fastened to the mixer arm and the other end free and equipped with a cut-out lug 54 projecting from the trailing edge of the arm (see Figs. 1 or 3), is flattened by the downward movement of the plunger 52, thereby sliding the lug toward the outer end of the mixer arm into the position shown dotted in Fig. 3. The mixer arm is then escaped under the stop bar 2'! to engage the operating lever 39. When, subsequently, the mixer arm is released to its upper position, the lug 54 engages the lower edge of the stop bar and carries it upward to its channel out position before the mixer arm escapes from the operating lever 39. External connections are made to the solenoid 5| by means of a two segment commutator 55 and a pair of brushes 56.

The apparatus for depressing the stop bars into The lever is entered in a slot channel in positions is shown in Figs. 1 and 2. It comprises a supporting bracket 51 and a brush arm 58 both secured to a shaft 59 which is rotated in a definite timed relation with the multiplex distributor. The brush arm traverses a pair of rings, one segmented 60 and the other solid 6|, each channel being associated with two of the segments of the ring 50. The bracket 5! serves as a support for a pivoted cut-inbar 62 and a solenoid 63 for the operation thereof. One terminal of the solenoid winding is grounded to the bracket 51 and the other connected to a slip ring 54 to which external connection may be made through a brush 65. The above described mechanism is referred to hereinafter as a clock and rotates as stated hereinbefore entirely independent of the mixer arm. The brush arms of the transmitting clock and a similar receiving clock are geared to or otherwise controlled by the transmitting and receiving distributors of the synchronous multiplex system in order to effect the simultaneous entry of a transmitter at the sending station and a receiving device at the receiving station.

The entry of a channel is effected while the mixer arm 20 is engaged with the stop bar 21 of any operative channel and only at such time as the brush arm 58 is in engagement with the segments of ring 69 corresponding to the channel desiring entry. At this time the cut-in bar 62 will be directly over the stop bar 2'! associated with this channel, so that the energization of the solenoid 63 actuates the cut-in bar to depress that particulr stop bar into its channel in position, thereby entering that channel into an operative relation with the line of traffic.

The mixer is also provided with apparatus having the function of periodically checking the subchannel arrangement at opposite ends of the lane of traffic. This apparatus comprises a gear 66 secured to the clock shaft 55 and arranged to drive another gear 61. A cam 88 is secured concentrically to the gear 61 for the purpose of controlling the operation of a set of contacts 69. The ratio of the gears is such that gear Bl makes one revolution for several revolutions of gear 56. Fig. 8 is a fragmentary top View of the cam and contact arrangement for the transmitting mixer and shows the cam 680. provided with a small raised portion 10 which, when engaged with the movable contact member 1|, effects the latters engagement with an auxiliary contact 72. Fig. 9 is a similar view for the corresponding apparatus for the receiving mixer. While the movable contact 13 is bearing on the cam surface M, this contact is engaged with an auxiliary contact 15. Contacts 13 and 16 are closed when the end of contact 13 drops into a notch H and when the contact 13 is bearing upon the cam surface 18, it is disengaged from both of the auxiliary contacts.

The co-ordination of the various functions of the mixer and clock is more thoroughly described in succeeding paragraphs dealing with the operation of the system in more detail. The pertinent parts of the mixer and clock are represented schematically in the figures relating to the aforementioned description, but in order to facilitate their identification, they will be given reference numerals corresponding to those used in the description of Figs. 1 through 9, but having a prefix of l as illustrated in Figs. 10 and 11 and a prefix 4 as illustrated in Fig. 12.

Referring to Figs. 10, 11 and 12 of the drawings, there is illustrated an expanding channel system utilizing a four-channel or quad-multiplex as the lane of traflic. The transmitting distributor of the synchronous multiplex at the first station is indicated at TD in Fig. 11 and the receiving distributor at the second station at RD in Fig. 12. The distributors are interconnected through the line circuit L arranged for duplex operationin accordance with the usual practice. It will be understood that ordinarily the system is also arranged for transmission from the second to the first station, the apparatus illustrated being duplicated for this purpose.

Referring more particularly to the transmitting apparatus shown in Figs. 10 and 11, the code combinations representing characters to be transmitted over the lane of traiilc are stored in the relay bank 80 comprising ten relays (in the case of a five-unit code) having armatures 8| to 99 connected through the armatures of relay 9I to the segments of channels A and B of the transmitting distributor TD or through the armatures of relay 92 to the segments of channels and D of said distributor, depending upon whether relay 9| or 92 is energized. The relays 9I and 92 are connected to segments 93 and 94 respectively of the local ring 96 of the transmitting distributor TD in such a manner that the relays are alternately energized whereby the characters stored in relay bank 80 are alternately transmitted over first one pair and then the other pair of channels of the transmitting distributor.

The operating windings 91 of the relay bank 80 are multipled to the contacts of the transmitters of the respective channels of the system, such as the tape transmitters 98, 99, I9I, I02, I93 and I04. The tape transmitters may be similar in construction to that shown in patent to Benjamin No. 1,298,440, dated March 25, 1919, except that transmitters 98, 99, IIII and I02 are provided with ten selecting contacts and the stepping magnet of each transmitter is arranged to step the tape two characters at a time whereby, upon each cycle of operation each transmitter is arranged to actuate relays of relay bank 80 in accordance with the code combinations representing two successive characters perforated in the tape. The transmitters may obviously be constructed in various ways to effect the transmission of two or more characters during each on the lane of trafiic upon the closure of the autostop contacts I I I controlled by the tape loop adjacent the transmitter. Each of the other transmitters is likewise entered under the control of its associated autostop contacts. The autostop contacts I I I are in series with one-half of the winding of the usual autostop relay II2, the mid-point of said winding being connected in series with the stepping magnet I I3 of, the tape transmitter 98. The autostop relay H2 is, normally energized when the associated tape transmitter is inoperative as indicated by the opening of the autostop'contacts I I I upon the shortening of the tape loop, the relay being locked up by the right hand half of its winding in series with the stepping magnet of the tape transmitter and through its contact I I4 to ground connected to the armature associated with said contact. Upon the lengthening of the tape loop and the resultant closure of the autostop contacts I I I, a circuit parallel to that just described is closed through the left hand half of the winding of relay II2, the contacts III, conductor I of cable II6, contact II1 of remote control relay II8, conductor 2 of cable H6 and conductor II 9 to ground at the contact I42I39 of the transmitting mixer TM. The autostop relay '2 becomes deenergized, the described circuit to ground through the contact H4 is opened and the right hand half of the winding of relay H2 is connected to ground through the contact IBI and the above described contact I42-I39 of the transmitting mixer. Thereupon a circuit is closed through the right hand outer armature I82 and back contact of the autostop relay M2 for entering the transmitter upon the lane of traffic in a manner to be described.

Assume that a group of transmitters having a preferred status, as described hereinafter, including transmitters 98, 99 and II, are operative, each having a sufficient quantity of perforated tape to permit the closure of their respective autostop contacts. The stop bars I21, I21a, I212), etc., corresponding to the operative channels, will be in their channel in positions as indicated in Fig. 10, and it will be apparent that the rotation of the mixer arm I20 will be stopped at some time by the engagement of said arm with the stop bar I21. When the local brush I83 engages segment I84 or I86 of the local ring 96 (depending upon whether the previously connected subchannel was connected to channels A and B or C and D of the transmitting distributor), a circuit is closed from battery through the conductor I81, the right hand armature and back contact of relay I88, the winding of magnet I35 and the normally closed contacts of relay I89 to ground, whereupon the magnet I35 momentarily depresses the mixer arm I20 to release the same from the latch member I21. As described in connection with Figs. 1-9 inclusive, the arm I29 then engages the inner end of the pivoted contact I39 and thereby momentarily removes the ground from the circuit of the stepping magnet transmitter 98, said circuit including the two parallel paths previously traced.

When the stepping magnet of the transmitter 98 is deenergized as described, the feeler pins of the transmitter are projected against the tape and the transmitter contacts are selectively operated in accordance with the characters perforated in the tape. operated into engagement with the upper or marking contacts I9I of the transmitter close circuits through corresponding operating windings 91 of relay bank whereby the code combinations are set up in the relay bank. The breaking of the circuit of magnet I95 by the continued movement of the brush I83 releases the mixer arm I29 which rises above the contact arm I39 as described and rotates into engagement with the stop bar of the next channel which is cut in, in this case I21a. The contact arm I39 being biased to closed position, recloses the circuit of the stepping magnet of transmitter 98,

whereupon the feeler pins of the transmitter are withdrawn from the tape and the tape is stepped to present the next two characters to the pins.

The contacts which are Upon the completion of the revolution of the mixer arm I20, the stepping magnet of the transmitter 98 is again deenergized by the actuation of contact arm I39 whereby the transmitter 98 is rendered operative to send two characters over the lane of traffic for each revolution of the mixer arm I20 as long as the stop or latch bar I21 is depressed. Likewise the mixer arm, during such revolution, causes the other transmitters which are cut in by the depression of their latch members corresponding to member I2! to be rendered operative in a predetermined order one after the other, the transmitters having nothing to send being passed by the mixer so that they do not occupy any lane time.

The two characters sent by each transmitter during its operative cycle are set up on the contacts of relay bank 80 comprising ten polar relays each having two unbiased armatures which remain in their operated positions. The armatures 8|, 8200 are arranged to transfer the code combinations received from the respective channels in response to the operation of the mixer alternately to channels A and B of the transmitting distributor TD represented by the first ten segments of the transmitting ring I92 and to channels C and D represented by the eleventh to t e twentieth segments of said ring, the change-over from one pair of multiplex channels to the other being effected by relays 9| and 92. The polar relays I93 havingtheir respective armatures connected to the segments of transmitting ring I92 are arranged to store the code combinations from relay bank 80 and impress marking or spacing potential on the segments of said ring so that the characters to be sent over channels A and B of said ring may be set up while the transmitting brush I94 is traveling over channels C and D, and vice versa. As shown, the marking potential of channels B and C is reversed with respect to channels A and D in order that transmission cannot be effected if the transmitting and receiving distributors are accidentally shifted 90, 180 or 270 out of phase, the out-of-phase relation being apparent from the distorted signals received. Obviously any other out-of-phase condition also interrupts communication.

The transmitters of the respective channels of the expanding channel system may be of any type adapted to operate in conjunction with the lane distributor and are preferably adapted for operation in accordance with characters stored in a tape or other storage medium under the control of the mixer. Each transmitter may be located in a patrons office and adapted to receive tape from a keyboard perforator or may be in the telegraph oflice and associated with a reperforator controlled from a keyboard transmitter in a branch oflice of patrons office.

7 When the transmitter 98 has completed the transmission of the message characters perforated in the tape, the channel is automatically disconnected from the lane of traffic and the lane time is divided between the remaining operating channels. The shortening of the tape loop opens the autostop contacts I I I whereupon the autostop relay II'l becomes energized and locks up in series with the stepping magnet of the transmitter 98, the locking circuit including the inner armature and contact I M of said relay. After the message characters stored in relay bank 80 from the channel or transmitter preceding transmitter 98 have been transferred to the transmitting distributor storage relays i93, the tongues 8I-90 and 8 I '--90' of relay bank are operated against their spacing or lower contacts by the restoring windings I06 energized from local segment I01 or I08 of the local ring M3.

The subsequent engagement of the mixer arm I20 with the stop or latch member I21 and the energization of magnet I35 operates the contact arm I39 as described above, but the stepping magnet of transmitter 98 does not become deenergized as during transmission from this channel since the stepping magnet is locked up through contact II4 of the autostop relay. Thus the armatures of relay bank 80 remain all spacing and the double-character exit signal in which both characters comprise five all-spacing impulses (blank character) is sent over the lane of traflic to cut out the receiving device of this channel in a manner to be described. The armatures 8I'90' of relay bank 80 constitute baffle circuits which are completed when theentry and exit signals are set up in a bank. Thus when the armatures 8i90' are all operated to spacing and remain in these positions after the mixer arm I20 has operated contact arm I39 on account of the energization of autostop relay II2 as described, a circuit is closed from battery through the armatures BI, 82', 83, 85, 85, 81', 88', 90', 89, and their respective spacing contacts, conductor I96, cut-out magnet I5I of the transmitting mixer TM, conductor I91, spacing contact and armature 84' to ground whereupon magnet I5I is energized. As previously described, the energization of magnet I5I is instrumental in effecting the movement of the stop bar I21 to its channel out position, or to its left hand contact I29 as viewed in Fig. 10. Thus the associated channel is cut out of operative connection with the line of trafiic. As the mixer arm I20 rotated, the remaining channels are cut out at the completion of each message in the same manner by the properly timed energization of magnet l5l.

The entry of each channel (of which that associated with transmitter 93 is illustrative) upon the lane of traflic as soon as a channel has message characters to transmit its effected automatically in response to the closure of the autostop contacts III as a result of the lengthening of the tapeloop from the associated perforator or reperforator. A circuit is thus closed from ground through the contact arm I39, conductor H9, conductor 2 of cable I I6, contact II! of relay I I8, conductor Iof cable I I5, the autostop contacts I I I and the left hand half of the winding of relay IIZ which is in parallel with the circuit through the right hand half of the winding of said relay, and the autostop relay H2 becomes deenergized, thereby removing the locking ground of the inner armature from contact II4 but closing a parallel circuit through contact I8I to the ground at contact arm I39 of the transmitting mixer. Upon the deenergization of relay IIZ a circuit is closed from segment I98 of the segmented ring I60 of the transmitting clock TC through the outer armature I82 and back contact of relay IIZ to ground at the stop or latch member I 21 through the left hand or channel out contact I29 which is in engagement with said latch member. When contact arm I58 of the transmitting clock reaches segment I98, the circuit is closed from the grounded segment I93 through contact ring ISI and the winding of relay I88 to battery, whereupon relay I88 becomes energized. When the contact arm I58 engages contact segment I99, a locking circuit is provided through the gizing' the cut in magnet I03 of the transmitting clock. As previously described, the energization of magnet I03 depresses the stop bar I21 into its channel in position. At the same time, as a result of the energization of coils I09 of relay bank 80, the entry signal is transmitted from the relay bank 80 to one pair of the channels of the transmitting distributor TD and the remote receiving device is cut in upon receipt of this signal in a manner to be described. It will be noted that the diversion of the local pulse from local ring 96 which normally energizes the magnet I 35 of the transmitting mixer prevents the transmission of characters from the channel which has been selected by the mixer arm I20 so that the transmission from this channel is delayed during the time required for sending the entry signals over the lane of traflic. Upon the next operating cycle, however, the characters which have been held up will be transmitted, since the mixer ar-m I20 has not been released from the stop member of the channel which it had selected.

In the embodiment of the invention illustrated, the double entry signal consists of two characters in which the fourth impulse is marking and the remaining impulses spacing (carriage return character). The energization of coils I09 of the fourth and ninth relays of relay bank 80 operates the armatures of the fourth and ninth relays to marking, the remaining armatures of the relay bank having been actuated to spacing by the restoring windings I06 in the manner described above.

The double entry signal consisting of two code combinations having the fourth impulse marking has been selected because this selection is ordinarily employed for carriage return and if used at all, need not be transmitted twice in succession. Obviously, any desired code combina: tion may be utilized as the entry signal although it is preferred that an entry signal be employed which is not normally used or at least is not required for regular communication. Another useful signal would be an upper case code combination such as figures shift followed by F.

As previously described, entry signals originate at the control apparatus in response to a channel desiring access to the lane. If, however, for any reason a double entry signal originates at a transmitter, means are provided for trapping such a signal, converting it into some other signal before it is transmitted over the line and thereby preventing the false entry of a receiving device for which there would be no correspond ing transmitter. Such a false entry signal is detected or read by a relay 202 and, being trapped in'this manner, is converted into some other signal combination by the relay 203.

Normally the relay 203 remains deenergized and the armatures 88 and 89 of the relay bank 80 are connected to corresponding segments of the distributor ring I 92. But the contacts of this relayv are arranged to, reverse these connections when the relay is operated, thus altering the signal combination actually transmitted fromthat set up on the relay bank 80. Under ordinary conditions of trafiic or when an entry signal properly originates at the control apparatus, the

relay 203 is not energized. However, when the armatures of the relay bank are positioned in response to an entry signal from either the control apparatus or from a transmitter, a circuit, comprising the armatures 8I, 82', 83', 85, 86, Bl, 83' and engaged with their spacing contacts, and armatures 04 and 89' engaged with their marking contacts, is prepared for the operation of relay 203. This circuit is not completed unless the entry signal is erroneously sent from a transmitter, in which case the impulse which operates the armatures 84 and 00' to their mark ing contacts also energizes the Winding 204 of relay 202 to close the contact 206. Closure of this contact completes the aforementioned circuit, effecting the operation of the relay 203 and thereby rendering the false entry signal nonfunctional for that purpose. It should be noted that relay 202 is provided with a restoring winding 20'! whereby the contact 206 is opened before each group of signal combinations is set up in the relay bank 80, thereby preventing the operation of relay 203 whenever a true entry signal is to be transmitted.

Referring to Fig. 12, the receiving distributor RD at the receiving station comprises a receiving ring 400 having the respective segments thereof connected to the windings of the relays of receiving bank MI, and local rings 402 and 403. Each of the relays in the relay bank 40! is a polar relay having two unbiased armatures adapted to remain in engagement with corresponding marking or spacing contacts after each impulse until the reception of an impulse of opposite polarity from the line relay. In this manner the code combinations received over the line are stored upon one set of armatures and the other set is arranged to close baffle circuits when the entry and exit signals are received.

The cable 404 which is multipled to the receiving reperforators or other receiving devices comprises ten conductors which are connected through the armatures of relay 406 alternately to the right hand armatures of the first ten relays of relay bank MI and to the right hand armatures of the remaining (11th to the 20th) relays of said bank. The relay 40B is energized as long as the distributor brush of the local ring 403 remains in engagement with the segment 40'! of said ring whereby the code combinations set up on the second half of the receiving relay bank are connected through the cable 404 to a receiv-.

ing device while the receiving distributor brush is resetting the first ten relays of said bank, and the last mentioned relays are connected through the back contacts of relay 406 and the cable 404 to another receiving device While the receiving distributor brush is resetting the eleventh to the twentieth relays of said bank in accordance with incoming signals.

The ten selecting windings of a reperforator, printer or other receiving or storing device, are represented at 408, said windings being connected through the individual conductors of a cable 409 to separate contacts 4 adapted to be simultaneously grounded by the pivoted normally open contact member 438 when the latter is engaged by the mixer arm 420 of the receiving mixer RM. If a ten-unit reperforator is employed, it may utilize a wide tape or-be arranged to step the tape two characters during each cycle of operation. The normally open circuits of the other receiving devices are similarly controlled, when the channels are cut in, by the mixer arm 420 under the control of the stop bars 421, 421a, etc. In general, the construction and mode of operation of the receiving mixer RM are similar to the construction and mode of operation of the transmitting mixer TM, the stop bars 421, 427a, etc., being depressed into the path of the rotating mixer arm when the channels are cut in and the mixer arm 42!! selecting the operative receiving channels one after the other in the same order and at the same time (taking the transmission lag into account) that the mixer arm I20 of the transmitting mixer selects the corresponding transmitting channels. The receiving devices of the operative channels are operated by momentarily closing the circuits, by the contact member 439, of the selecting windings 408 and of the usual operating magnet to print, store or perforate the characters set up at that instant on the connected group of relays of the receiving bank 45!.

As has been described above, the entry signal which is transmitted over the line to enter a receiving device on the expanding channel system comprises two successive characters, each having only the fourth impulse marking (double carriage return). This signal may be sent over either channels A and B or channels C and D depending upon the time when the clocks TC and RC reach a subchannel which is to be cut in.

Assuming that the entry signal is received on channels A and B of the receiving distributor represented by the first ten relays of the receiving bank 40!, as the brushes of the receiving distributor continue to travel, the circuit of relay 4% is interrupted at the local segment 45! of the distributor. Upon the deenergization of relay 4H5 during the time when the received signals are being stored in the channels C and D of the receiving bank 401, a circuit is closed through the upper armature and back. contact of relay 4%, through the left hand armatures and marking contacts of the fourth and ninth relays of relay bank 451, the spacing contacts of the first, second, third, fifth, sixth, seventh, eighth and tenth relays of bank 4!! i, through the winding of relay M2, brush arm 458 and segments MI and M3 of the receiving clock, left hand channel out contact 429 and the stop bar 42! to ground, whereupon relay 4| 2 becomes energized.

It will be noted that this circuit is only closed upon the transmission of the entry signal, and the position of the brush arm 453 of the receiving clock, when said signal is received, determines the receiving device which is to be entered on the channel, said device corresponding to the ransmitter 98, Fig. 10, in this instance. The selection of the proper receiving device or chan-- nel is thus determined as stated above by the time of transmission of the entry signal. A short signal with interspersed traffic signals is thus operative to select any one of a large number of channels. The lane of traffic is utilized for message signals While the brushes of the clocks move on to the next point of entry which may be hundreds of message characters farther on. The significant lapse of time to effect proper entry is not wasted.

Relay 4H2 remains locked up through the segment 494 of the receiving clock, the latter circuit including the left hand armature and front contact of said relay, On the continued movement of the brush arm of the receiving distributor RD,

a circuit is closed through the local segment 416, the right hand armature and front contact of relay 402 and the entry magnet 463 of the receiving clock RC. In a manner similar to the entry of a transmitter, the energization of magnet 463 depresses the stop bar 421 into its channel in position. As soon as the brush arm 458 of the receiving clock RD leaves the segment 414, the locking circuit of relay 412 is interrupted and the relay is restored to normal. During the time the relay M2 was energized, the circuit of the operating magnet 435 of the receiving mixer RM was interrupted at the right hand armature and back contact of said relay, thereby preventing release of the mixer arm 420 from the stop bar with which it was engaged.

In this manner the characters forming the entry signal on channels A and B are prevented from reaching a receiving device and the transmitting and receiving apparatus is maintained in synchronism since, as has been described above, transmission of regular character signals over the lane of traflic is momentarily interrupted during the transmission of the entry signal. If the entry signal had been received on channels C and D of the receiving distributor, the operation would have been substantially as described except that relay 456 is energized when the 'local brush of the distributor engages segment 45'! of the local ring 463, and the baffle circuit for reading the entry signal comprises upper armature and front contact of relay 496 and contacts of the eleventh to the twentieth relays instead of the first to tenth relays of relay bank 45!.

Upon the subsequent engagement of the mixer arm 42!) with the stop bar 421, the selections stored in one half of the receiving bank 45! are connected through the contacts of relay 455 to the windings 488 of the receiving device which is operated by the closure of the contacts 4! I and 439 when the mixer arm 428 is depressed beneath the stop bar 421 by the magnet 435. The circuit of the magnet 435 includes the armature and front contact of relay 4 which is operated as long as any of the stop bars are operated to the right in their channel in positions, the right hand armature and back contact of relay 412 and segment M5 or MB of local ring 402 of the receiving distributor RD. Each of the receiving channels which has been cut in is thus rendered operative concurrently with the corresponding one of the transmitting channels connected successively to the lane of traflic under the control of the transmitting mixer TM irrespective of the number of operative channels, the entire lane time being divided among the operating channels when more than a predetermined number of channels are operative.

Inaccordance with a further feature of the invention transmission from certain of the transmitters may be made dependent upon the operation of other or regular channels of the system which will be referred to as preferred channels. Thus for example in Figs. 10 and 11 the transmitters I02, I03 and IE4 may be deferred trafiic transmitters and arranged to seize a channel of the expanding channel system only when there are none or any other predetermined number of the preferred channels in operation. The deferred channels may be precisely the same as regular channels except that a relay contact is inserted in each of the auto-stop circuits of these transmitters which will bid for entry or exit of the deferred channels when the preferred channels in operation have been reduced to the predetermined number. The auto-stop circuit for the transmitter I02 includes a contact 208 of relay 299 for the above described purpose. It will be understood that this relay will have similar contacts for each of the other deferred channel transmitters. Transmitters I 93 and I 04 having different tapes are five-unit transmitters arranged to operate in unison on one expanding channel. Corresponding five-unit receiving devices may be employed at the receiving end of such an expanding channel.

Associated with the stop bars I21, IZ'Ia, etc. of the transmitting mixer TM are individual contacts 2H which are connected to separate resistances 2I2, 2l3 and 2M. Resistances 2I2 which are associated. with preferred channels have a common terminal which is connected through the operating windings of relays 289, 2H3, 2H and I89. It will be apparent that the current through these relays varies according to the number of preferred channels which have been cut in. Similarly, resistances 2I4 have a common terminal which is connected only to the windings of relays 2i! and I89. Thus, it is seen that the current through the windings of relays 209 and 2M3 is always in direct proportion to the number of preferred channels which are cut in, whereas the current through the windings of relays 2i! and I89 is in direct proportion to the total number of channels cut in including both preferred and deferred channels. The relay 209 is arranged to remain operated as long as one or more preferred channels is cut in and to release when there are no preferred channels cut in. The relay 2I'I is adapted to close a contact when the number of operative channels is less than three. Similarly, the relay I89 is adapted to close a contact when one or more channels is cut in.

When no channels are cut in, the armature of relay I89 remains on its right hand contact and the mixer arm I spins freely without being depressed by the armature of magnet I 35, thus preventing the actuation of any of the contact arms I39. When any stop bar such as bar I2'I is moved to the channel-in position by the clock mechanism, a circuit is established through the operating winding of relay I89, the left hand resistance 2I2, through the right hand contact 2H and the stop bar I21 to ground. Positive battery is applied to the other terminal of the winding of relay I89, the circuit for which may be extended to a remote point such as an operating position or a subscribers ofiice and carried through a meter or similar indicating device 2I8 for a purpose to be described. Relay I89 is provided with a biasing circuit which has a tendency to move the armature to its right hand contact. However, the current which is conducted through the operating winding of this relay by means of the described circuit when one or more channels is cut in, is sufficient to overcome the effect of the biasing circuit and move the relay armature to its left hand contact, thereby preparing the operating circuit for magnet I35. Thus. the mixer arm of the transmitting mixer resumes its regular function when the first channel is entered.

If several channels are in operation at once, the speeds of the various expanding channel transmitters are comparatively slow. Let us assume that three channels of the first station give a satisfactory rate of operation for each channel, even though the multilever transmitters were capable of keeping the circuit completely full. In that case the one busy operator would find it extremely diflicult to keep the line full of traffic and therefore it is desirable to limit the speed of operation of the channel transmitters when the number of channels cut in is less than three. Relay 25'! is also provided with a biasing circuit having a tendency to move the armature 2I9 to its right hand contact. However, when three or more transmitters are out in, the preponderance of current through the operating winding of this relay maintains the armature on its left hand contact. With two transmitters cut in on the expanding channel system, the biasing circuit of relay 2I'I becomes effective to move the armature of this relay to its right hand contact. The armature of this relay is connected by means of conductor I3 of cable H6 through an armature and back contact of relay H8 to ground. As soon as armature 2I9 engages its right hand contact, this ground is applied to a conductor 28I. which is connected to the front contacts associated with the outer armatures of all of the auto-stop relays such as armature I82 of relay I I2 and armature 282 of relay 283.

If it be assumed that relay 283 is energized and locked in a manner similar to that described for relay H2, armature 282 extends the ground connected to its front contact to segment 284 of the transmitting clock TC. Similar segments associated with all of the transmitters which are disabled by reason of the fact that their associated auto-stop relays are operated, are grounded by the operation of relay 2II. The grounding of these segments results in the movement of one of the stop arms I 27a, I2'Ib, etc. into its channel in position as described. Consequently the stop bar corresponding to one of the cut-out channels is actuated as if the channel were being entered upon the system for communication purposes and since the transmitting mixer TM does not step to a new position during the entry function, the rate of transmission for the operating channels is curtailed. Thus, the relay 2!? constitutes a kind of governor device on the re ular channels which remain in operation.

As soon as one of the stop bars I2! is actuated to its channel-in position by the operation of relay 2| 1, ground is applied to another one of the resistances 2I2, H3 and 2M which results in an increase in the current through the operating winding of the governor relay 2II. Since at this time there are again three of the stop bars in their channel-in positions, the operating current of relay 2H is greater than the biasmg current and the armature 2| 9 is moved to its left hand contact. When the mixer arm I29 reaches the stop bar associated with the inoperative channel which has been actuated in re sponse to the action of the governor relay, an all spacing signal combination is sent from this transmitter since its stepping magnet remains locked up under the control of the associated au'tostop relay and the stop bar is moved to its channel-out position in the manner previously described. If in the meantime there have been no additional channels entered, the armature 2I 9 of the relay 2!! will again be moved to its right hand contact and the above described cycle of operations will be repeated. It will be noted that when the stop bars associated with the deferred channel transmitters are actuated to their channel-in positions by the-action of relay 2II, no transmission occurs from these transmitters even though there may be an appreciable'accumulation of tape awaiting transmission so that their associated autostop contacts are closed...;.These I channels cannot be entered for the transmissionv of traffic until their respective autostop circuits. are completely closed. These circuits. are ar-l,

ranged to be closed onlywhen there are no preferred channels in operation. Forexample, the

autostop circuit for transmitter ")2 is extended by conductor 1 of cable H8 through a back contact and armature of relay H8 to conductor 8 of cable I I8 and this circuit stands open at contact.

288 of relay 209.

When none of the preferred channels is in op. eration the current through the winding of relay.

289 is reduced to zero permitting the armatures of this relay to move to their respectiveback contacts. The autostop circuits for all of the deferred channel. transmitters are through contacts of relay 289. Consequently. it is, seen that as soon as the preferred channel transmission has ceased. .all of the deferred channel transmitters having tape prepared for transmis-. sion are given an opportunity to be entered on the system. For example, if it be assumed that transmitter E82 is supplied with a quantity of tape so that its autostop contacts are closed, the closure. of contact 288 of relay 289 complete- 1y closes the circuit of the autostop relay whereby this relay is released and its associated trans.-. mitter placed under the control of the transmit-,

ting mixer TM. The stop bar corresponding to this channel is moved to its channel-in position as described and .transmission is effected over this channel by the operation of the. transmitting mixer arm I28. other deferred channels having .traflic to send are entered and the deferred trafiic is carried carried In a similar manner all customer may -.be.bille d forthe actual number of message. characters transmitted.- irrespective of the time required to send these characters. Such 'a. metering arrangement is desirable, particularly on channelsv providing a preferred serv- I him solely on the'basis of the length of time he' is connected to a circuit.

Another metering arrangement is one by which a customer may-be billed in accordance with the total number of characters transmitted, the

charge for each character beingweighted in accordance with the busy condition'of the line. It

will be apparent that when a largenumber-of channels is operating over the line a given portion of the line .timeis more valuable than the same portion taken at a time when the line is comparatively idle. Consequently it may be desirable in some cases to provide a subscriber over the system as long as there are none of the preferred channel transmitters desiring entry on.

the system.

Deferred channel transmitters I03 and I84 are of the standard five-contact variety and though employed in transmission of two separate messages their magnets are in series and their operation is in all respects equivalent to that of the other transmitters. At the receiving end the devices for receiving impulses transmitted by the transmitters I03 and I84 may be the usual five unit printers or reperforators both connected to one group of contacts of the receiving mixer. The governing action of relays I89, 2|! and 288 and their associated circuits need not be repeated at the receiving end in connection with the receiving mixer RM and the receiving clock RC as the time consumed in the cut-in and deferred channel functions are identical in all respects to those employed for the'operation of the regular channels.

Another important feature of th invention is the metering or service charge arrangement which is made for the customers having transmitting apparatus in a system of this nature. Several forms of metering arrangements are shown in this application. In one form the metering device is a counter 286, the operating circuit for which is connected in series with the operating circuit of the stepping magnet H3 of transmitter 98. The counter may be a conventional electro-magnetic register having counting wheels operated by the successive energization and deenergization of the operating magnet. Thus, every time the transmitter stepping magnet is deenergized and subsequently energized for the transmission of message characters, the number of such characters is automatically registered on the meter285. In thismanner the with a type of metering service whereby he can select the maximum rate which heis willing to pay for thetransmission of his traffic. For this purpose such a channel is provided witha meter 23'! which ma be'similar. to a conventional integrating watt hour meter. One of the windings 288 of this meter is connected in series with relays 2|! .and I89 whereby thecurrent is in direct proportion to thenumber of operating channels. A second winding 289'is connected to a make contact 29! on the transmitting mixer TM. .With this arrangement every time the mixer arm I28 engages the contact arm l39d to actuate the deferred channel transmitters I83.

and |84,ia circuit is closed through the make contact 2,9lg'and through winding 289 of themeter 281. Thus, successive operations of .these transmitters. produce a series of impulses through winding 289 of the'meter. Both meter windings have a cooperative action on the register mechanism and. since the'current through the winding 288 is in proportion to the number of channels which are entered. the series of impulses through winding 289 is weightedin proportion to thebusy. conditioner the line. It will be noted that the Winding 288 of the meter 281 is connectedin serieswith the windings of relays. 289 and.2l6 when the armatures of relay 289 are in engagement with their front contacts so that the current flowing in this-series circuit is proportional. only to the number of preferred channels which-are entered. However, when there are no preferred channels in operation the. armatures of relay .289 are released. and the winding 288 of relay 281 is connected to a fixed potential so that the current through thiswinding will have a fixed minimum value which may be considered as a minimum rate given to deferred channels.

A subscribermay be givenv an opportunity to select. the maximum .rateto be paid for the transmissionoof .his trafiic and for such purpose is provided with a relay 216 having an operating winding which is connected in series with the multipled resistances 2I2 associated with preferred channels. This relay also has a biasing winding 292, which is connected to positive potential through the'winding of a relay 293 and is extended to the subscribers ofilce' or remote operating position where it is connected through a meter or equivalent device 294 and through a rheostat 296 to ground. Relay 2l6 has contacts which are inserted in series with the auto-stop relay associated with the channel transmitter. The tendency of the biasing circuit of the relay is to move the relay armatures to their respective right hand contacts. ,The current through the operating winding, on the other hand, has a tendency to move these armatures to theirrespective left hand contacts. The result of this arrangement is that whenever the current in the biasing circuit becomes greater than that in the operating circuit, the auto-stop circuit is closed and the channel entered on the system. The subscriber is given controlof the biasing current through the rheostat 296. He is also provided with an indication'of the busy condition of the expanding channelsystem by'rneans of the meter 2l8.

Assume that there are eight preferred channels operating over the system and that a subscriber who is given a choice ofrates has traffic which he desires to transmit. However, the maximum rate whichhe is willing to payjis one which is based on theutilization of the lane by sixchannels. The meter 2l8 indicates a rate number of preferred channels is reduced to five the biasing circuit of the relay becomes effective ingly less.

to move the armatures to their right hand con- 7 tures to their left hand contacts when the chan nel is entered and that fact is registered by the movement ofv its associated stop bar to its channel-in position whereby the current throughthe operating winding of the relay 2l6 is increased. The additional biasing given to this relay is only sufficient to compensate for the entry of one additional preferred chanrieL-which' in this case is the channel of the subscriber desiring; entry at this point. It is thus seen that there are now six channels in operation and as, soon as one or more other preferred channels is entered, relay 2l6 operates its armatures totheir left hand contacts and the channel controlled thereby is disconnected from the expanding channel system until such time as conditions again become favorable for entering the channel;

Thus it is seen that a subscriber who is provided with means for choosing the maximum rate which he is willing to pay for transmitting his traffic is entered on and remains connected to the system as long as the channel cut-in conditions are'suchthat his, rates do not exceed'a maxiimum value. With an arrangement of this nature such a subscriber is also provided with means to'take advantage of any lower rates if the number of channels is decreased. For exami rth m ximu rat h sen i ase on. the operation of the expanding channel system ferred subscribers. traiiic. seenthat the armatures of relay 209 were released ig-'35s withsixjchannels operating and one or more of the operatingchannels is cut" out the value of the current in the winding 288 'of the recording meter 281 is reduced accordingly, The effect of this reduction is that the characters counted by such a meter are given less weight and the totals registered by the meter are correspond- Thus, a subscriber may choose the maximum rate at which he will be billed for the transmission of his traffic and at the same time willbe able to obtain the advantage of any prevailing rate under the pro-selected maximum.

The constants of the, circuits of relay 2|6 are adjusted so that a subscriber, by moving the arm of the rheostat 295 to its extreme left hand position, may be given an unqualified preferred status irrespective of the number of other preferred channels which may be cut in. In this case the current through the biasing circuit of relay 2I6 is in excess of the maximum current in the operating circuit so that the armatures of this relay are permanently engaged with their respective right hand contacts and the transmitter 'associatedwith this channel is given a status equal to that of the preferred channel transmitters 98, 99 and. 10!. Hence, whenever such a subscriber has material to be transmitted, his channel is immediately cut in on the system and the line time is shared among this channel and any other preferred channels which may also be cut in at this time. .Itwill be noted, however, that the rate which is charged such a subscriber is based upon the number of characters trans mitted and the busy condition of the system. It is obvious that as other preferred channels are cut in and cutout of the system during the connection of such a channel this rate will fluctuate.

In series with the biasing circuit of relay 2E6 is the winding of a relay 293, the armature of which is connected to the resistance 2l3 associated with the mixer stop bar corresponding to this channel. The relay 293 is adapted to maintain this armature in engagement with this front contact so long as the current is suflicient to prevent the operation of the armatures of relay 216 to their right hand contacts while one or more preferred channels is cut in. The front contact of relay 293 is connected to the common terminal of the resistances 212 so that as long as relay 293 is operated the resistance unit 233 is included in the group of preferred channel resistances. Hence, the release of relay 209 while any of the preferred channels, including the channel having control of its maximum rates, is prevented thereby preventing the operation of any of the deferred channels. However, when the subscriber moves the arm of his rheostat 296 to its extreme right hand position, he elects to defer the transmission of his traffic until such time as there are no preferred channels in operation and the group of deferred channels is given an opportunity to send. This manipulation of the rheostat adjusts the current through relay 293 so that its armature is released to its back contact. Now it is seen that the resistance H3 is switched to a connection with the common terminal of the deferred channel resistances 2M. Under these conditions transmission from transmitters H33 and IM can occur only when there are no preferred channels in operation. For this class of service a fixed minimum rate may be charged for the transmisison of the de- It was previously aescjssscz to their respective back contacts for the operation of deferred channels. minimum rate which is charged the subscriber utilizing transmitters I83 and I64 is provided by adjusting the current through Winding 288 of the meter 28! to a fixed minimum.

Another equitable basis for the rates which are charged for the transmission of the sub scribers trafiic is recording the time that he is associated with the expanding channel system. This arrangement'recognizes the fact that the rates should be a function of the number of characters transmitted and of the busy condition of the system. A subscriber having a given number of characters to transmit will be able to move this trafiic over the system faster when the system is relatively idle than when it is busy. Since the line time required to transmit one character during a busy condition of the system has a greater value than the time required to send a character when the system is lightly loaded, a record of the time-during which a channel is connected for operation will provide a fair basis for charging the subscriber. Such a metering arrangement is provided for one of the channels by connecting in series with one of the resistances 2| 4 the winding of a relay 3ti. Whenever the channel associated with Hence the. fixedthis resistance is entered upon the system, relay 3! is energized. The engagement of the armature of this relay with its front contact closes a contact from a source of power to a metering device 309. Such a device may be similar to a conventional self-starting synchronous electric clock. The dial of the device may be graduated in any convenient manner so that the-indication is in proportion to the time that the subchannel is connected to the system. .It will be obvious to those skilled in the art that the metering device 360 may be arranged to integrate over any desired period of time. so that the total time taken over a substantial periodduring which the channel is connected to the system may be'obtained.

It is obvious that any of the forms of metering combinations be considered as coming within the scope of the instant invention.

It is desirable in a system of this character to provide auxiliary signaling or control channels in addition to the channels used for communication. These auxiliary channels may be used for various purposes such as signaling between the attendants at the respective oflices or for controlling the operation of the equipment in any desired manner. Thus, if difficulty is experienced in reception at one office it may be desirable to stop transmission into that ofiice.v trolling channel may be used, for example, to

' stop the apparatus and reconnect the operative channels one by one from an inoperative condition to insure that the same number .of transmitting and receiving channels are in operation.

In the system shown these signaling or control channels are provided with space on the. transmitting and receiving mixers as in the case of each of the communication channels.

If the attendant at the station shown in Figs.

If desired the con.-

10 and 11 wishes to stop transmission coming into that station from the station shown in Fig;

12, he operates a: switch or key 5.302 ;to itsleithandut I58 of the'clock-reaches this segment a stop bar 121g is moved to its channel-in position and an ant to the fact that his transmission is being.

interrupted. These control circuits are shown in detail in Fig. 10 and since it is understood that the system is arranged for full duplex operation and each-station is supplied with both trans.- mitting and receiving apparatus it will be'understood that theoperation of relay I I8 is effective to interrupt all transmission from the station of Fig. 12 to the station of Figs. 10 and.

11. The opening of the autostop circuits of the transmitters results in the movementof all of the stop bars associated with operative channels to their channel-out positions. When'the transmitting mixer TM engages the contact arm associated with the signaling channel an all-spacing character is transmitted, since there is no apparatus associated with this arm, and the stop bars of the signaling channel are also movedto their channel-out positions. This may occur immediately following the entry of the signaling channel on the system since there is no time relation between the clock arms and the mixer arms. However relay H8 is arranged to maintain the armatures in an operated condition for a period of time sufficient for the mixer arms to make a complete circuit-irrespective of the numberof channels which may be operating.- This slow-to-release characteristic of this relay may be obtained in any well known manner. As. soon asthe armatures of this relay are released to their back contacts following the movement of all .of the stop bars to their channel-outpositions, the I operative transmitters are again entered on the system one at a time. Since it is assumed that the multiplex apparatus is in syn- .chronism, the transmitting and receiving clocks are also in step with one another and the entry of the channels of the system will necessarily be correct.

The operation of an auxiliaryv signaling chan- -nel in accordance with the foregoing description requires that an entry signal and an exit be sent over the lane of traffic. If, at the receiving station of Fig. 12, the stop bar 4219 is arranged in the manner of the stopbar 21" of Fig. 4, it will be moved to its channel in position to energize the relay H8 in response to a received entry signal and, immediately thereafter, moved to its channel out position by means of the retractile spring. In this case it is obvious that valuable lane time will not be used for the transmission of an exit signal for an auxiliary signalling channel provided With such facilities. Consequently, at the transmitting station, the auxiliary signaling channel need not be equipped with a stop bar on the-mixer. It will be understood by those skilled in the art that such a 1 1: position thereby applying ground to segment-303 of the transmitting clock :TC..= qWhen the arm channel may be used for any desired form of signaling between the attendants at the terminals ofisuch. a system.. .For example;- the-relay I i8 instead of controllingther auto stop .circuits of to control a bell or any other type of signal The stop bar 421g may also be similar to the stop bar 21" of Fig.3. In this case, once it has been moved to its channel in position in response to a received entry signal; the circuit controlled thereby remains closed, thereby maintaining in operation any signal devices connected thereto until an attendant responding to the signal device restores the stop bar manually to its channel out position. Also, it is seen with this type of stop bar no exit signal transmitted over the lane of traffic is required and no stop bar is needed on the mixer at the transmitting station. l

Provisions are also made in this system to checkperiodically the channels connectedto the system. Such a check is made over a second control channel by the closure of a contact 305 effected by the engagement of the transmitting clock cam I10 with its associated follower !1!. Ground is thus applied to' segment 306 of the transmitting clock and a stop bar H1 is moved to its channel-in position. The entry of this channel is similar to that of any of the 'communication channels so that at the receiving station a corresponding stop bar 421i is'moved to its right hand contact corresponding to the channel-in position of this bar. If the multiplex apparatus is in synchronism, the transmitting and receiving clocks are in step and the movement of the stop bar 421) to its right hand contact occurs at a time when the receivingcam follower 413 is about to be engaged by the depressed portion 411 of the cam 4158b. At this time the follower 413 is disengaged from both of its contacts. 'As soon as the engagement with the depression 411 occurs the follower is en-' gaged with its lower contact. It will be noted that a connection is made from the cam follower contact 413 to one side of the Winding of relay 4B! which is connected in series with the winding of relay H8 and to positive potential. The engagement of the cam follower contact 413 with its lower contact is ineifective at this time since the stop arm 421 is engaged with its right hand contact. Further movement of the cam 468D restores the follower contact 413 to its intermediate position in which it stays for a period of time sufficient for the transmitting and receiving mixer arms to make a complete revolution when all of the channels are entered on the system. The purpose of such an arrange ment will be described in greater detail in a subsequent portion of the specification. The fact that relays 48! and H8 were not operated at the time that the cam follower contact 431 engaged its lower contact is an indication that the multiplex apparatus and the clocks are in synchronism. I

During the time that the contact 413 is held in its intermediate position following its engagement Withits lower contact, the mixer arms will" reach the stop arms associated with the control channel. At the transmitting station the engagement of mixer arm I2!) with the contact arm !39 releases relay 301. The inner left hand armature of this relay connects through its back contact positive potential to one terminal of the winding of-the exit magnet The engagement of the outer armature of this relay with its back contact connects a ground to the other terminal of-this magnet winding. The energization of the exit magnet at this. time moves the stop bar I21 toits channel-out position. i The of contacts to operate relay 483.

aeeaeteq engagement-of the'other armatures of-relay 361 with their'respective back contacts sets up; a signal in the relay. bank Bllfor transmission to the remote station. The signals sent under these conditions are preferably difierent from the entry and exit signals used for the communication channels and they also should be signals of a character or function which does not occur twice in succession in ordinary trafiic. For the purposes of this description the character Y' has been chosen. If the system is found to be operating correctly by the periodic check so that the transmitting and receiving mixers as well as the clocks are in step, the receiving mixer arm 42!! will be engaged at this time with the contact arm 4391 associated with the receiving end of the control channel. Hence the double Y signal combination which is received is applied to a receiving bank of relays 482. This relay bank is equipped with a set of contacts which are interconnected in such a manner that the reception of the double Y connects the ground of the lower armature through the reading circuit to the right hand contact of the upper set Relay 484 is also operated by the engagement of the contact arm 439i with its associated contacts. Hence, a circuit is established from. battery on the from contact of relay 483 through its armature and the front contact of relay 484, through its armature to the winding of the exit magnet 45!. In this manner the stop bar 421i is moved to its channel-out position against its left hand contact. It will be remembered that at this time the contact follower 413 is being held in its intermediate position so that there is no operation of relays 48! and 8'.

Thus it is seen that the operation of the periodic checking mechanism controlled by the cam apparatus associated with the transmitting and receiving clocks results only in the simultaneoirs entry of the transmitting and receiving portions of the control channel and also the subsequent exit of the control channel. The gearing on the respective cams is such that this periodic check is made once in every several revolutions of the clocks depending upon the requirements of a particular circuit. This period may correspond to the time required'to send as many as several hundred characters. It has been shown that, with the 'systemoperating properly, the entry and exit of the control channel .is ineffective to produce any change in the system. However, there are several conditions under which the periodic checking function is effective to interrupt the operation of the system. when it is found to be operating abnormally.

If the multiplex apparatus is out of synchronism so that the transmitting and receiving clocks are not in step, the entry of the control channel from the transmitting end of the system will-not connect the receiving apparatus of this channel. Consequently at the receiving station the stop bar 421; will be engaged with its left hand or channel-out contact at the time that the cam 468D reaches the point where the follower contact 413 is moved into engagement with its lower contact. In this case the ground which is connected to the stop arm is connected through the lower contact and the follower 413 to the operating circuits for relays 48! and H8. The operation of the latter relay discontinues transmission from' the station shown in Fig. 12 to-the station shown in Figs. 10 and 11 and the 411815. These characters areapplied to the-relay channels, operating inthis direction are disconnected as described; The operation of'relay 48! applies a ground through the normal contacts of a switch 302, corresponding to-switch 382 at the other station. Thus, operation of this relay is effective to initiate control-signalwhich, when received atthestation shown in Figs. IOand 11, operates the remotecontrol'relay 8.. Since a similar function-has been described in detail, the performance of this function in the opposite direction from that described isshown diagrammatically. The reception of the control signal at the other end of the circuit energizes the receiving entry magnet 463 to 'move the stop bar 421g which in turn operates the relay M8 to disconnect the transmitting apparatus. It may be thatwith themultiplex apparatus out of synchronism, this transmitted stopv signal will not be properly received at :the station shown in Figs. and 11. However; this communication channel is also provided with periodic taking facilities which will operate as described to stop transmission in the other direction also. The receiving portion of such apparatus is shown fragmentarily and includes the cam 4681)", which operates the contact 413' which in conjunction with stop arm 421 controls the operation of relays 48! and H8. Armatures 3G8 and tilt indicate diagrammatically the operation of the reading relay bank 482 to control respectively the operation of relays MI and H8 and the exit magnet 45l'. If desired, the periodicity of the tests made over both channels of the duplexed circuit may be different to guard against circuit failures whichmay cause one stations transmission to be received by the same station. With thetransmittingand the receivin clocks out ofsynchronism it may be that in response to an entry signal the control channel stop bar 421) is moved to its channel inposition in place bank 482 and their respective ,armatures are moved to one or the other oftheircontacts in accordance with the. received character. combination. Since the character combination is something other than a double Y,,one or more "of the armatures of this reading bank will be moved to a contact connected to a conductor 486. Consequently the ground connected to the the operating channels are disconnected from the system and subsequently reconnectedone at a time.

The operation of the reading bank of relays 432 is also effective to detect a condition wherein the stop bar 421 of the control channel is erroneously moved to its channel-in .position. Such a condition may be the result of the mutilation of a character signal when it is being transmitted over the line in such a manner that it is transformed into an entry signal. ,Consequently such a signal is utilized at the receiving end for thepurpose of entering whatever channel happens to be associated with the receiving clock at the time that the signal is received. Obviously no harm will be done if this channel is one which is already entered on the system but if the .ohannelwhich is entered under these conditions of a regular communication channel; Thismay occur at anytime while the cam follower 4'53 is bearing on the raised portion of the cam so that the follower is engaged with its upper contact. It is seen that the movement of the stop bar 421 to its right hand contact in response to a false entry signal connects a ground through the cam contacts to the operating circuits of relays 48! and H8 thereby stopping transmission in both directions and disconnecting all channels from the system. At the expiration of a period of time long enough to effect the disconnection of all channels, relays 48! and H8 are released thereby permitting the reconnection of all channels.

The channel arrangement of the system may also be incorrect without the multiplex apparatus being out of synchronism. That is, the transmitting and receiving clocks may be in step with one another but for one reason or another the transmitting and receiving mixers may be out of step. Such a condition may arise from a variety of different circumstances such as the connection of more channels at one end of the system than at the other, etc. The fact that the transmitting and receiving clocks are in step means that when the periodic test is initiated by the connection of the control channel to the system, stop bar 421i will be moved to its channelin position at the proper time. But because the transmitting and receiving mixers are out of step the receiving mixer operates the contact arm 439 of the control channel at the time that the transmitting mixer arm is sending communication characters from one of the regular chanis the control channel this fact is detected by the first character which is received on this channel.

The receiving circuits of the relay bank 482 operate -for this purpose in a manner similar to that described.

The nature of the invention may be ascertained from the foregoing description of an illustrative embodiment, it being understood that changesin the inventionherein disclosed may be made within the scope of'what is'claimed with out departing from the spirit of the invention.

What is claimed is:

1. An expanding channel telegraph system comprising a plurality of communication channels and means whereby at least a part of the transmitting time of an idle channel is utilized by another channel, a lane of trafiic shared by operative channels, means for integrating the message characters sent on each channel, and means for weighting the integrated characters in accordance with the busy condition of the lane of traffic.

2. An expanding channel telegraph system comprising a plurality of channels and means whereby at least a part of the transmitting time of an idle channel is utilized by another channel, a lane of traflic shared by operative channels, means for registering the number of message characters transmitted on each channel, means for registering the frequency of transmission of said message characters, and means for combining the registered information.

3. A telegraph system comprising a plurality of channels, control means for said channels whereby the rate of transmission of message characters on any channel is dependent upon whether more or fewer other channels are in operation, means for metering the trafiic on said channels on the basis of the number of characters transmitted and a variable scale of charges per character, and means for varying said scale of charges in accordance with the number of channels in operation,

. two element electric device for metering traiiic on said channels, means. including one of said elements for integrating the number of message characters transmitted, and means including the t other of said elements for integrating the number of channels operating over the lane of traflic.

5. A telegraph system comprising a lane of trafiic, a plurality of communication channels,

means for 'operatively associating with said lane of traflic those of said channels having message characters to transmit, each operative association being only for a period required to transmit said characters, control means whereby the rate of. transmission of message characters onany channel operatively associated with said' lane of traffic depends upon the number of other channels. operatively associated with the lane of traffic; and mean for timing the periods of the operative association of. each channel with. the lane of traffic. Y 6. A system of communication comprising a a, lane ,of traific, ,a plurality of communication channels, control means for. apportioning the transmitting time of said lane oftraific among those of said channels having signals to transmit, and metering means for determining the proportional part of the transmitting time of said 1 lane of traffic utilized by each of said channels during a period of time, said metering means including atiming device associated with one of said channels and rendered operative only during the signal transmitting intervals of its associated channel.

, 7 A system oi communication comprising a laneof trafiic, a plurality of communication channels, control means for dividing'the transmitting time of said lane of traffic among operative channels, and means for metering traflic on said channels on the basis 01" the number of characters transmitted and the proportional part of the transmitting time of said lane of traffic utilizedby said channels, said metering means including a unitary integrating device having two cooperative elements, one responsive to the number of characters transmitted and the other responsive to the busy condition of the lane.

8. A system of communication comprising a lane of trafiic, a plurality of communication channels, control means for dividing the transmitting time of said lane of trafiic among operative channels, means for metering traffic on the basis of the number of characters transmitted, means for determining the rates to be charged for said metered traflic on the basis of the utilization of said lane of trafiic by the operative channels, and means for rendering operative one of said channels when the rates do not exceed a predetermined maximum.

9. An expanding channel telegraph system comprising a plurality of channels and means whereby at least a part of the transmitting time of an idlechannelis utilized by another channel, a lane of traffic shared by operative channels,

means for metering traffic on the basis of the characterized by means for varying the rate of said one channelwhen operative in accordance with the utilization of the lane of trafiic by the operative channels.

PHILO HOLCOMB, J R. 

